I spent a day finding out first-hand what it's like to take part in an experiment aimed at devising new treatments for obesity. I'm a "control", providing baseline metabolic data against which the two experimental groups can be compared. But it involves a lot more than filling in a questionnaire and twiddling your thumbs, as I found out. Andy Coghlan

Time to measure how fit (or not) I am. First I'm fitted with a belt carrying sensors and electrodes that will measure how efficiently I burn oxygen. Then the treadmill. I've never been on one of these before (except the one called the news department at New Scientist). It starts off at a stroll, builds to a canter and ends in a heart-pounding frenzy, not helped by the clippy thing on my nose that forces me to breathe through my mouth into the attachment. But I manage to survive, even when it feels like I'm in the Grand National. Metabolic assistant Laura Watson is pointing approvingly to the chart, telling me my peak oxygen consumption is normal. Or something. I'm too tired to take it in!